Wilms tumor is a childhood neoplasm affecting about 1/10,000 children under the age of 10. A number of genetic loci and inherited conditions, particularly overgrowth syndromes such as Beckwith-Wiedeman and Simpson-Golabi-Behmel syndromes, are known to predispose to Wilms tumor. A study is underway to determine the extent to which other types of tumor are present in the families of a child with Wilms tumor. The results will be used to evaluate risks to relatives of Wilms tumor patients and to identify at risk families for further study.